add a basic filtering example (#128)

* add a basic filtering example

* use modern C++ initialization

* fix english

Author: mmomtchev

example/api2-samples/api2-decode-filter.cpp

@@ -0,0 +1,235 @@
+#include <functional>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <set>
+
+#include "audioresampler.h"
+#include "av.h"
+#include "avutils.h"
+#include "codec.h"
+#include "ffmpeg.h"
+#include "packet.h"
+#include "videorescaler.h"
+
+// API2
+#include "codec.h"
+#include "codeccontext.h"
+#include "filters/buffersink.h"
+#include "filters/buffersrc.h"
+#include "filters/filtergraph.h"
+#include "format.h"
+#include "formatcontext.h"
+
+using namespace std;
+using namespace av;
+
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+        return 1;
+
+    av::init();
+    av::setFFmpegLoggingLevel(AV_LOG_DEBUG);
+
+    string uri{argv[1]};
+
+    ssize_t videoStream = -1;
+    VideoDecoderContext vdec;
+    Stream vst;
+    error_code ec;
+
+    int count = 0;
+
+    {
+
+        FormatContext ictx;
+
+        ictx.openInput(uri, ec);
+        if (ec)
+        {
+            cerr << "Can't open input\n";
+            return 1;
+        }
+
+        cerr << "Streams: " << ictx.streamsCount() << endl;
+
+        ictx.findStreamInfo(ec);
+        if (ec)
+        {
+            cerr << "Can't find streams: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+
+        for (size_t i = 0; i < ictx.streamsCount(); ++i)
+        {
+            auto st = ictx.stream(i);
+            if (st.mediaType() == AVMEDIA_TYPE_VIDEO)
+            {
+                videoStream = i;
+                vst = st;
+                break;
+            }
+        }
+
+        cerr << videoStream << endl;
+
+        if (vst.isNull())
+        {
+            cerr << "Video stream not found\n";
+            return 1;
+        }
+
+        if (vst.isValid())
+        {
+            vdec = VideoDecoderContext(vst);
+
+            Codec codec = findDecodingCodec(vdec.raw()->codec_id);
+
+            vdec.setCodec(codec);
+            vdec.setRefCountedFrames(true);
+
+            vdec.open({{"threads", "1"}}, Codec(), ec);
+            // vdec.open(ec);
+            if (ec)
+            {
+                cerr << "Can't open codec\n";
+                return 1;
+            }
+        }
+
+        // Setup filter
+        Filter filter_buffer_src{"buffer"};
+        Filter filter_buffer_sink{"buffersink"};
+        FilterGraph filter_graph;
+
+        // Input and ouput contexts
+        std::stringstream src_args;
+        src_args << "video_size=" << vdec.width() << "x" << vdec.height() << ":pix_fmt=" << vdec.pixelFormat()
+                 << ":time_base=" << vdec.timeBase() << ":pixel_aspect=" << vdec.sampleAspectRatio();
+        clog << "Input arguments: " << src_args.str() << endl;
+        FilterContext src_ctx = filter_graph.createFilter(filter_buffer_src, "in", src_args.str(), ec);
+        if (ec)
+        {
+            clog << "Error creating filter source context: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+        FilterContext sink_ctx = filter_graph.createFilter(filter_buffer_sink, "out", "", ec);
+        if (ec)
+        {
+            clog << "Error creating filter sink context: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+
+        // Setup the filter chain
+        filter_graph.parse("scale=320x200", src_ctx, sink_ctx, ec);
+        if (ec)
+        {
+            clog << "Error parsing filter chain: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+        filter_graph.config(ec);
+        if (ec)
+        {
+            clog << "Error configuring filter chain: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+
+        // Setup the entry/exit points
+        BufferSrcFilterContext buffer_src{src_ctx};
+        BufferSinkFilterContext buffer_sink{sink_ctx};
+
+        while (Packet pkt = ictx.readPacket(ec))
+        {
+            if (ec)
+            {
+                clog << "Packet reading error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+
+            if (pkt.streamIndex() != videoStream)
+            {
+                continue;
+            }
+
+            VideoFrame frame = vdec.decode(pkt, ec);
+
+            count++;
+            // if (count > 100)
+            //     break;
+
+            if (ec)
+            {
+                cerr << "Error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+            else if (!frame)
+            {
+                cerr << "Empty frame\n";
+                continue;
+            }
+
+            // Push into the filter
+            buffer_src.addVideoFrame(frame, AV_BUFFERSRC_FLAG_KEEP_REF, ec);
+            if (ec)
+            {
+                clog << "Filter push error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+
+            // Pull until there are no more incoming frames
+            VideoFrame filtered;
+            while (buffer_sink.getVideoFrame(filtered, ec))
+            {
+                filtered.setTimeBase(frame.timeBase());
+                auto ts = filtered.pts();
+
+                clog << "  filtered: " << filtered.width() << "x" << filtered.height() << ", size=" << filtered.size()
+                     << ", ts=" << ts << ", tm: " << ts.seconds() << ", tb: " << filtered.timeBase()
+                     << ", ref=" << filtered.isReferenced() << ":" << filtered.refCount() << endl;
+            }
+            if (ec && ec.value() != -EAGAIN)
+            {
+                clog << "Filter pull error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+        }
+
+        clog << "Flush frames;\n";
+        while (true)
+        {
+            VideoFrame frame = vdec.decode(Packet(), ec);
+            if (ec)
+            {
+                cerr << "Error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+            if (!frame)
+                break;
+
+            // Push into the filter
+            buffer_src.addVideoFrame(frame, ec);
+            if (ec)
+            {
+                clog << "Filter push error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+
+            // Pull until there are no more incoming frames
+            VideoFrame filtered;
+            while (buffer_sink.getVideoFrame(filtered, ec))
+            {
+                filtered.setTimeBase(frame.timeBase());
+                auto ts = filtered.pts();
+                clog << "  filtered: " << filtered.width() << "x" << filtered.height() << ", size=" << filtered.size()
+                     << ", ts=" << ts << ", tm: " << ts.seconds() << ", tb: " << filtered.timeBase()
+                     << ", ref=" << filtered.isReferenced() << ":" << filtered.refCount() << endl;
+            }
+            if (ec && ec.value() != -EAGAIN)
+            {
+                clog << "Filter pull error: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+        }
+    }
+}